1. Field of the Invention
This invention relates to current limiting cartridge type fuses having a portion of restricted diameter in one end cap which serves as a rejection feature. A portion of reduced diameter in the cap, when used in conjunction with special fuse holders designed to accept only fuses having such reduced diameter section, prevent the insertion of fuses with inadequate voltage or interrupting ratings in such fuse holders.
2. Description of the Prior Art
Electric cartridge fuses having rejection grooves or portions in one terminal cap are well known in the Prior Art. Such fuses satisfy the requirements of Underwriters Laboratories Class R fuses as well as Canadian Standards Association (CSA) HRC fuses.
A representative electric fuse design which illustrates a fuse having a rejection ferrule is disclosed in U.S. Pat. No. 4,344,058 entitled LOW VOLTAGE CARTRIDGE FUSE DESIGN to Edward J. Knapp, Jr. and Richard J. Perreault and assigned to the assignee of the present invention. In the '058 patent, no active portion of the fusible element extends into the fuse cap region beyond the region of reduced cross-section which defines the rejection feature.
U.S. Pat. No. 2,321,711 entitled FUSIBLE ELECTRIC PROTECTIVE DEVICE to Elmer H. Taylor discloses a dual element cartridge fuse having a centrally positioned overload interrupting portion of the fusible element with short circuit interrupting portions of the fusible element extending from opposite ends of the overload portion to the fuses end ferrules.
The present invention makes possible the incorporation of a dual fusible element arrangement such as that shown in the '711 patent in a cartridge fuse design having an end ferrule which has a rejection groove therein.